A meeting among the spirits of Hogwarts to decide matters concerning them.

"[Peeves] wanted to attend the feast — well, it's quite out of the question, you know what he's like, utterly uncivilized, can't see a plate of food without throwing it. We held a ghost's council — the Fat Friar was all for giving him the chance — but most wisely, in my opinion, the Bloody Baron put his foot down."

—Sir Nicholas informs the Gryffindor students about the latest ghost's council.[src]